Identities and accounts¶
In order to be an active participant on the Concordium blockchain (e.g., hold, send, receive Global Transaction Unit (GTU)) a user must create an account.
The user will get an Initial Account at the same time as an identity has been issued by an identity provider. As the initial account is submitted to the chain by the identity provider, said identity provider will know the owner of the initial account. For this reason, the user may consider not using the initial account, and create a regular account instead.
Regular accounts’ owner is not known to the identity providers, or any other single entity. To facilitate compliance with relevant regulations, a regular account can only be created from an identity which is issued Off-chain by an Identity provider. While an account has to be created from an identity, the user’s privacy is still protected, and the account owner’s identity can only be revealed via the process of anonymity revocation, which can only happen under stringent regulations, such as upon a court order. In particular, a key feature of the design of identities and accounts is that the identity provider cannot reveal the identity of an account on their own.
Anonymity revocation can only happen in exceptional circumstances (e.g., if authorities have detected suspicious activity on the account) and requires action by one or more anonymity revokers and the identity provider who issued the account’s identity.
Obtaining an identity¶
Identities are issued by an identity provider. There is a registry of approved identity providers publicly accessible from the Concordium blockchain, with their contact information. Concordium Foundation will maintain the list in the beginning.
Each identity contains a number of cryptographic values, and a number of user-chosen attributes, such as nationality or country of residence. These attributes are certified by the identity provider. The cryptographic values are a number of public and private keys, a signature from the identity provider, as well as a number of secret values the user must use to be able to use the identity to create accounts.
Identities can be created via Concordium ID. Identity issuance requires Identity Verification, which is the process of verifying the real-life identity of the user. This will typically involve taking photographs, scans of identification documents (e.g., passport), etc. Identity verification also checks that the user-chosen attributes are valid for the user.
Concordium ID (mobile wallet) identity¶
In the testnet phase the Concordium ID app supports two identity issuance flows: Notabene and Notabene (development). In both cases the identity provider is Notabene, but the identity verifiers differ.
The Notabene flow is supported by Onfido and requires the user to take photos of themselves, as well as supporting documentation such as a passport, driver’s license or identity card. The identity attributes are determined based on the provided documentation.
The Notabene (development) flow allows the user to provide their own attributes and does no verification. This flow is available for testing purposes, and will not be supported on the Mainnet.
Creating an account¶
Once a user has an identity, they can use it to create a number of accounts, besides the Initial Account created by the identity provider upon creating the identity. In contrast to obtaining an identity, opening an account is an On-chain action and requires sending a transaction to a node participating in the Concordium network. The input to the transaction is a credential which contains a number of cryptographic proofs, as well as a selection of attributes the user wishes to reveal publicly. The proofs establish that the attributes the user revealed publicly are the ones approved by the identity provider. The proofs reveal no other information. In particular, the identity provider itself cannot determine the owner of the account. (Revealing the owner is only possible through anonymity revocation, which requires the identity provider and anonymity revokers to act together.) Note that revealing attributes publicly is completely optional. The benefit gained from revealing attributes is that other users may decide whether to trust the account based on the publicly available information.
Every account on the chain must be derived from an identity that is verified and signed by an approved identity provider. It is publicly visible which identity provider issued an identity for an account, and who the anonymity revokers are for the account and the identity. In addition to this basic information which enables regulatory compliance, an account owner can choose to publicly reveal other values on their account, such as their nationality or country of residence. Since this information is publicly accessible anybody can check it before interacting with an account. Moreover, being able to see who issued the identity enables whoever wishes to interact with an account to judge the level of risk in the transaction.
When necessary, the anonymity revokers and identity provider can work together to determine the owner of an account and determine which accounts belong to the same owner. (They should only do so when legally obliged to, such as by a court order.) Anonymity revocation is a two-stage process requiring cooperation of multiple parties.
Each account has an encryption of a specific user identifier. This number can be decrypted by sufficiently many of the anonymity revokers working together. (The set of anonymity revokers and the number of them required to decrypt the user identifier are determined when the identity is issued.)
Once the user identifier is decrypted the identity provider can look up the real-life identity of the owner of the account.
After step 2 the anonymity revokers can additionally decrypt a value that is held by the identity provider and allows the revokers to find all accounts the user has created from a given identity. Additionally, this value allows anonymity revokers to see the amount of GTUs in the shielded balance of de-anonymized accounts.
All of these actions are subject to rules and processes, and only the relevant entities learn any information about the account owner. No information is publicly revealed.